Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751855AbaBQVGh (ORCPT ); Mon, 17 Feb 2014 16:06:37 -0500 Received: from mx1.redhat.com ([209.132.183.28]:26083 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751097AbaBQVGe (ORCPT ); Mon, 17 Feb 2014 16:06:34 -0500 Subject: Re: [RFC][PATCH 0/5] arch: atomic rework From: Torvald Riegel To: paulmck@linux.vnet.ibm.com Cc: Linus Torvalds , Will Deacon , Peter Zijlstra , Ramana Radhakrishnan , David Howells , "linux-arch@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "mingo@kernel.org" , "gcc@gcc.gnu.org" In-Reply-To: <20140217202324.GJ4250@linux.vnet.ibm.com> References: <20140213002355.GI4250@linux.vnet.ibm.com> <1392321837.18779.3249.camel@triegel.csb> <20140214020144.GO4250@linux.vnet.ibm.com> <1392352981.18779.3800.camel@triegel.csb> <20140214172920.GQ4250@linux.vnet.ibm.com> <1392486310.18779.6447.camel@triegel.csb> <1392666947.18779.6838.camel@triegel.csb> <20140217202324.GJ4250@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Date: Mon, 17 Feb 2014 22:05:58 +0100 Message-ID: <1392671158.18779.6909.camel@triegel.csb> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2014-02-17 at 12:23 -0800, Paul E. McKenney wrote: > On Mon, Feb 17, 2014 at 08:55:47PM +0100, Torvald Riegel wrote: > > On Sat, 2014-02-15 at 10:49 -0800, Linus Torvalds wrote: > > > On Sat, Feb 15, 2014 at 9:45 AM, Torvald Riegel wrote: > > > > > > > > I think a major benefit of C11's memory model is that it gives a > > > > *precise* specification for how a compiler is allowed to optimize. > > > > > > Clearly it does *not*. This whole discussion is proof of that. It's > > > not at all clear, > > > > It might not be an easy-to-understand specification, but as far as I'm > > aware it is precise. The Cambridge group's formalization certainly is > > precise. From that, one can derive (together with the usual rules for > > as-if etc.) what a compiler is allowed to do (assuming that the standard > > is indeed precise). My replies in this discussion have been based on > > reasoning about the standard, and not secret knowledge (with the > > exception of no-out-of-thin-air, which is required in the standard's > > prose but not yet formalized). > > > > I agree that I'm using the formalization as a kind of placeholder for > > the standard's prose (which isn't all that easy to follow for me > > either), but I guess there's no way around an ISO standard using prose. > > > > If you see a case in which the standard isn't precise, please bring it > > up or open a C++ CWG issue for it. > > I suggest that I go through the Linux kernel's requirements for atomics > and memory barriers and see how they map to C11 atomics. With that done, > we would have very specific examples to go over. Without that done, the > discussion won't converge very well. > > Seem reasonable? Sounds good! -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/